Mice — they’re just like us!
A group of researchers at Tokyo University of Science have found that mice, after watching their fellow mice be sad, become sad themselves.
In a study published in the journal “Behavioural Brain Research,” scientists explain how they determined the rodents empathized with their suffering species mates to the point where they, too, suffered.
First, they put two mice of different sizes into a cage together, then prompted the smaller mouse to irritate the larger one, causing it to become aggressive. Meanwhile, in a nearby cage, a third mouse bore witness to the bullying. Despite not being directly bullied, researchers found that after 10 days of watching it, the witness mouse subsequently began showing signs of depression.
“They weren’t interested in other mice, which is unusual, as mice are sociable creatures,” lead study author and pharmaceutical sciences professor Akiyoshi Saitoh told Vice. As well, “If you give mice the choice of drinking sweet or regular water, they will almost always go for the sweet drink because it’s more enjoyable. But the mouse that witnessed social defeat didn’t, which indicated a decreased desire for pleasure.”
These depressive symptoms didn’t follow a linear trajectory for all of the witness mice. Some became depressed and recovered only to again become depressed a month later.
“Mice experiencing secondhand social defeat didn’t make sudden, full recoveries once they were removed from that stress setting, placed back into their normal environment and treated with antidepressants. Alarmingly, some developed their symptoms again, but four weeks later,” Saitoh said.
Saitoh and his co-authors hope their findings can bring more awareness to the complex ways in which human depression impact not just those in the throes of it but those around them.
“The number of individuals suffering from depression has been on the rise the world over. However, the detailed pathophysiology of depression still remains to be elucidated,” he said in a press release, adding to Vice, “I want people to think about how stress can not only change the brains of those with depression, but can change ours—those watching—as well.”